Is it ok to caramelise foods.

Personally I find it OK to do this, I like to have caramalised carrots and parsnips with a roast.

So far I have found that adjusting my insulin slightly seems to work (for me about 2 units more) but of course everyone is different

You don't say if your are on insulin or not. This could be a bit more tricky if not.

My idea would be to try it (at home) and test after your meal and see if you notice much of a difference. The only way to know for sure I guess

It won't add sugar, it will make the sugars more easily available so may be absorbed more rapidly so causing a higher spike.
It's a matter of try and see how much it affects you.

I have fried onions almost on a daily basis AND cooked in butter without affecting my BG's

Really, the only way to find out is trial by meter as we are all individual and what affects one might not necessarily affect another